Thornless blackberry named &#34;Per Can&#34;

ABSTRACT

A Nordic-type blackberry variety named &#34;Per Can&#34; combines the characteristics of cold-hardiness, thornless branches and stems, adaptability to various soil conditions, vigor and strength, absence of suckering, and ease of propagation by tissue culturing. Per Can yields berries characterized by an excellent taste (slightly acid, slightly sugary), a very fresh appearance and appealing texture, with a real blackberry aroma and no noticeable aftertaste.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinctive cultivar ofblackberry plant named Per Can. This cultivar belongs to the genusRubus, which also includes a number of soft fruits, such as raspberries,loganberries, gooseberries, currants and achenes, cultivated forculinary purposes. The typifying characteristics of these soft fruitsare well-known from various publications, including "Soft Fruits," 2 THEBIOCHEMISTRY OF FRUITS AND THEIR PRODUCTS, pages 375-377 (1971).

Species of blackberry plants vary in color, size, shape, acidity, andother commercially important and botanically significantcharacteristics. For example, R. allegheniesis has many small drupelets,while R. frondosus is more rounded and has comparatively fewer.Blackberries frequently bear flowers and fruit simultaneously, and fruittends to ripen randomly on the canes.

Origin of the Variety

The new cultivar of the present invention was developed by me in Laval,Canada, as a selection derived from Rubus canadensis; the cultivar isthus not a hybrid. The wild growing Canadian parent was collected on theAppalachian plateau, in southern Quebec. This parent grows in thornlessor nearly thornless populations.

In developing Per Can, I selected six completely thornless specimens ofR. canadensis from the wild population. After two years of propagation,over 50% of the best seedlings were totally thornless. Three additionalyears of propagation through very cold winters resulted in a singlethornless plant have superior winter hardiness. It produced normalfruits during mid- to late-summer (July-September) in southern Quebec.

This new cultivar must be asexually reproduced by tip-cutting or tissueculture. Both methods give good results, but commercial propagation isvery much faster by tissue culture. The absence in this cultivar ofsuckers precludes propagation by root cuttings. The "Per Can" thornlessblackberry has been asexually reproduced. For commercial requirements,the propagation to produce a stable variety has been made by tissueculture at Congdon & Weller Wholesale Nursery Inc., in the state of NewYork.

DESCRIPTION OF THE PHOTOGRAPHS

The accompanying photographs illustrate the color and other features ofthe new cultivar, showing it in various stages of fruit maturation.

Sheet 1 is a view of a blackberry bush of the Per Can variety, showingthe fruit in different stages of maturity.

Sheet 2 is a close-up view of a cane of the variety, also showing thefruit in different stages of maturity.

Sheet 3 shows the variety with unripened fruit and, in addition,provides a good view of the leaves of the plant.

Sheet 4 is a closeup view of unripened fruit of the variety.

Sheet 5 is a view of the mature fruit of the variety.

DESCRIPTION OF THE VARIETY

The Nordic-type cultivar of the present invention exhibits excellentresistance to temperatures as low as -40° F., and was the mostcold-hardy among many others tested. Also, it is thornless, whichobviously makes cultivation and harvesting easier and enhances itcommercial potential. Per Can adapts well to various soils, but prefersneutral (approximately pH 6.8) to acid soil.

While both tip-cutting and tissue culturing are conventional propagatingtechniques for the genus Rubus, tissue culturing is the preferred modeof reproducing Per Can because virus-free propagation is therebyassured. Tissue culturing thus utilizes artificial nutrient media underaseptic (pathogen-free) conditions in controlled laboratoryenvironments. See Murashige, "Plant Propagation Through TissueCultures," Ann. Rev. Plant Physiol. 25: 135-66 (1974), the contents ofwhich are hereby incorporated by reference.

In general terms, tissue culture is divided into four stages ofdevelopment. The first stage (stage 1) entails establishing a sterileculture of a portion (explant) of the stock plant. During stage 2 thereis a stimulation of multiple shoot development, which usually involvestransferring cultured material to a medium with containing levels of theplant hormone cytokinin. Stage 3 involves preparing the culturedmaterial for removal from culture, a process that typically entailsexposing the material to increased auxin levels to initiate roots onshoots which were multiplied in stage 2. Finally, cloned plants areadapted to greenhouse conditions during stage 4, in the course of whichthere is always a gradual reduction of humidity until the plants arehardened off.

With regard to the Per Can cultivar, stage 4 usually includes rooting,that is, the variety of the present invention can be rooted directly instage 4; accordingly, stage 3 is optional. The specific details of Rubuspropagation are otherwise conventional, as disclosed, for example, byAnderson, In Vitro 15 (3): 177 (1979), and Acta Hort. 112: 13-20 (1980);by Pyott and Converse, Hort. Sci. 16(3): 308-309 (1981); and by Snir,Scienta Hort. 14: 139-143 (1981), the respective contents of whichdocuments are hereby incorporated by reference.

Prior to maturity, the fruit of the Per Can variety has a reddish color.When fully ripe, the fruit has a dark black color identified with color202A of the Royal Horticultural Society (RHS) Colour Chart. The leaves,when fully developed, have a yellow/green color, corresponding to color147A of the RHS Chart, and are simple, first leaves are three-lobed,further appearing leaves are five-lobed. Leaves are slightly pubescenton both sides. During the maturing process, the leaves have a yellowishperiphery.

The plant canes are two-toned. More specifically, the portion of thecanes are two-toned. More specifically, the portion of the cane exposedto the sun has a grey/purple color corresponding to RHS color 183C. Theshaded portion of the cane is yellow/green, with a color correspondingto RHS color 144B. (The color evaluations described herein were made inSt. Eustache, Quebec, Canada, on the morning of Aug. 24, 1987, at 9:30a.m. Viewing was effected in direct sunlight, under dry, coolconditions, when the temperature was about 60° F.).

As shown in the table below, chemical analyses reveal substantialdifferences between Per Can and typical cultivated blackberry varieties.These analyses involve comparisons of pH, Brix value (percent of solublesolids), acidity (percent of citric acid found in the berries) andhumidity (percent of moisture).

                  TABLE                                                           ______________________________________                                                                 Acidity                                                              Brix     (%) Citric                                                                              Humidity                                              pH   Value    Acid      (%)                                        ______________________________________                                        Per Can Variety                                                                            3.36   9.1      0.84    87.68                                    Typical Cultivated                                                                         3.0    8.9      trace   84.8                                     Variety*                     amounts                                          ______________________________________                                         *Values derived from "Soft Fruits," loc. cit., at Tables II and V.       

One of the major soluble components of blackberries and other soft fruitis its sugar. The sugar-to-acid ratio is important in determining flavorand commercial acceptability. Sensory evaluations indicate that Per Canyields berries characterized by an excellent taste (slightly acid,slightly sugary). There is no noticeable aftertaste, and the fruit hasreal blackberry aroma. It also has a very fresh appearance and appealingtexture.

Per Can is vigorous and strong, not suckering. Canes are biennial,trailing, and may reach a length of about 12 feet (350 cm) in good andheavy garden soil. Growth is slower and less vigorous in sandy soil,with canes reaching about 5 feet (150 cm). Typically, the variety needstrellising to control growth. The variety produces drupelets of about 6millimeters in diameter. Seeds of the variety have a flattened kidneyshape, and average 4 millimeters in length, 3 millimeters in width and1.5 millimeters in thickness.

The largest leaves of the variety are basal, averaging 19 to 32centimeters in length. Leaf size decreases at higher positions on thestem, averaging 20 to 22 centimeters in length at the top of the stem.Leaf sizes are measured from the base of the petiole.

Firmness of fruit of the variety (Newtons) has been measured at43.0±3.8. Juiciness has been measured at 80.0%±3%.

Inflorescenses of Per Can are glandless, white and produced in clustersof more than 30 from June until September in northern temperateclimates. Fruits ripen from mid-July to late October in this zone. Theberries are round and slightly conical (length: about 30 mm; diameter:about 20 mm). The weight of one berry ranges from about 4.5 grams toabout 8.7 grams with the average weight of one berry being about 4.5grams.

The variety should be planted in sunny and dry locations on trellises orwire supports, spaced about 10 inches apart. Per Can is useful for homegardens, as well as "pick-your-own" and contract growing. Afterharvesting, all canes that produced fruit, i.e., those that are twoyears old, should be pruned. In addition, (cut-out) one year-old canesshould be thinned and tied to trellises or wires.

In colder zones, the canes should be laid on the ground and, ifnecessary, protected with mulch. Canes should be tied to wires thefollowing growing season, and the plants should not be fertilized afterthe beginning of August.

I claim:
 1. A new and distinct cultiver of Rubus canadensis, named PerCan, as herein shown and described, characterized particularly as touniqueness by the combined characteristics of cold-hardiness, thornlessbranches and stems, adaptability to various soil conditions, vigor andstrength, absence of suckering, and ease of propagation by tissueculturing.